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Friday, November 12, 2010

Starting and Stopping Jetty Gracefully with Groovy and JMX

I'm working on a project that uses Tapestry and ActiveMQ together; it works great on my Mac, but on my client's Windows workstation, ActiveMQ doesn't shut down cleanly and corrupts its local files pretty consistently.

Unfortunately, there isn't a way (using RunJettyRun, the Eclipse plugin for Jetty) to gracefully shutdown Jetty. You just pull the plug on it, mid execution.

Looking for a solution, I realized that Jetty can expose most of its internals via JMX; this would allow us to start it up and shut it down cleanly in development.

So, I created a Groovy LaunchApp class to launch Jetty with JMX enabled:

package com.example.main

import java.lang.management.ManagementFactory 

import org.eclipse.jetty.jmx.MBeanContainer 
import org.eclipse.jetty.server.Server 
import org.eclipse.jetty.webapp.WebAppContext
import org.slf4j.LoggerFactory

 * Alternative the RunJettyRun Eclipse plugin that allows greater control over how Jetty starts up.
class LaunchApp {
 static PORT = 8080
 public static void main(String[] args) {
  def LOG = LoggerFactory.getLogger(LaunchApp.class)
  LOG.info "Starting up Jetty ${Server.getVersion()} instance on port $PORT ..."
  def server = new Server(PORT)
  server.stopAtShutdown = true
  server.gracefulShutdown = 1000 // 1 second
  def context = new WebAppContext()
  context.setContextPath "/"
  context.setWar "src/main/webapp"
  server.setHandler context
  def mBeanServer = ManagementFactory.getPlatformMBeanServer();
  def mBeanContainer = new MBeanContainer(mBeanServer);
  LOG.info "Join the fun at http://localhost:$PORT/landing"
  LOG.info("Jetty instance has shut down")
... and a Groovy StopApp class:
package com.example.main

import javax.management.ObjectName
import javax.management.remote.JMXConnectorFactory
import javax.management.remote.JMXServiceURL

 * The flip-side of {@link LaunchApp}, this tool locates the running Jetty instance and uses JMX
 * to request a graceful shutdown.
class StopApp {
 static JMX_PORT = 8085
 static JMX_URL = "service:jmx:rmi:///jndi/rmi://localhost:$JMX_PORT/jmxrmi"
 public static void main(String[] args) {
  println "Shutting down Jetty instance"
  def connector = JMXConnectorFactory.connect(new JMXServiceURL(JMX_URL), null)
  connector.connect null
  def connection = connector.getMBeanServerConnection()
  def on = new ObjectName("org.eclipse.jetty.server:type=server,id=0")
  connection.invoke on, "stop", null, null 
  println "Shutdown command sent"   

The only trick is to ensure that LaunchApp's JMX MBean server is exposed for access, so you need the following system properties set:


Thursday, November 04, 2010

First Rule of LinkedIn: Customize the Message

As far as social networks go, I like LinkedIn a lot. Nice site, lots of features, generally quite useful. In fact, I like it enough to be careful about who I link to ... for example, I only link to people I've met in person (or, at least, had a phone conversation with).

For some people, social networks are a game and the score is the number of connections. Thus, I get a fair number of "cold" link requests.

Here's a trick: if you want someone like me to link to you, you need to customize the message. It better say something like "Hey Howard, we hung out at JavaOne last year." or "I attended your talk on Clojure." or something else real and personal or it's quite, quite, likely to be deleted immediately.

Monday, November 01, 2010

Tapestry 5.2.2

... and the latest version of Tapestry, 5.2.2, is now available. This is the second beta release for Tapestry 5.2, addressing a few bugs in 5.2.1, and adding a couple of minor non-disruptive improvements ... read about it in the release notes.

Tapestry 5.2.2 is available for download, or via Maven:


I expect some minor issues will be addressed in Tapestry 5.2.3. Expect that in a week or so.